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JavaScript Reserved Words

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In JavaScript, certain words are off-limits for use as variables, labels, or function names.

abstract arguments await* boolean
break byte case catch
char class* const* continue
debugger default delete do
double else enum* eval
export* extends* false final
finally float for function
goto if implements import*
in instanceof int interface
let* long native new
null package private protected
public return short static
super* switch synchronized this
throw throws transient true
try typeof var void
volatile while with yield

Words with a * were introduced in ECMAScript 5 and ECMAScript 6.

Learn more about various versions of JavaScript in the section JS Versions.

Removed Reserved Words

The ECMAScript 5/6 standard no longer includes the following reserved words:

abstract boolean byte char
double final float goto
int long native short
synchronized throws transient volatile

Avoid using these words as variables. Not all browsers fully support ECMAScript 5/6.

JavaScript Objects, Properties, and Methods

Avoid using the names of built-in objects, properties, and methods in JavaScript.

Array Date eval function
hasOwnProperty Infinity isFinite isNaN
isPrototypeOf length Math NaN
name Number Object prototype
String toString undefined valueOf

Java Reserved Words

JavaScript is commonly used alongside Java. It's recommended to steer clear of certain Java objects and properties when naming things in JavaScript.

getClass java JavaArray javaClass
JavaObject JavaPackage

Other Reserved Words

JavaScript is a programming language that can be utilized in various applications.

Steer clear of mentioning HTML and Window objects and their properties in your code.

alert all anchor anchors
area assign blur button
checkbox clearInterval clearTimeout clientInformation
close closed confirm constructor
crypto decodeURI decodeURIComponent defaultStatus
document element elements embed
embeds encodeURI encodeURIComponent escape
event fileUpload focus form
forms frame innerHeight innerWidth
layer layers link location
mimeTypes navigate navigator frames
frameRate hidden history image
images offscreenBuffering open opener
option outerHeight outerWidth packages
pageXOffset pageYOffset parent parseFloat
parseInt password pkcs11 plugin
prompt propertyIsEnum radio reset
screenX screenY scroll secure
select self setInterval setTimeout
status submit taint text
textarea top unescape untaint
window

HTML Event Handlers

Additionally, refrain from using the names of all HTML event handlers.

Examples:

onblur onclick onerror onfocus
onkeydown onkeypress onkeyup onmouseover
onload onmouseup onmousedown onsubmit
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